Unless otherwise indicated herein, the description provided in this section is not prior art to the claims and is not admitted to be prior art by inclusion in this section.
A typical cellular wireless network includes a number of base stations that each radiate to define one or more coverage areas, such as cells or sectors, in which user equipment devices (UEs) can operate and engage in communication over an air interface with the cellular wireless network. Each base station may then be coupled with network infrastructure that provides connectivity with one or more transport networks, such as the public switched telephone network (PSTN) and/or the Internet for instance. Within this arrangement, a UE operating in a coverage area of the cellular wireless network can engage in communication, via the cellular wireless network, with remote network entities or with other UEs operating in the cellular wireless network.
The cellular wireless network will generally operate in accordance with a particular air-interface protocol or “radio access technology,” examples of which may include Orthogonal Frequency Division Multiple Access (OFDMA (e.g., Long Term Evolution (LTE)), Code Division Multiple Access (CDMA) (e.g., 1×RTT and 1×EV-DO), Wireless Interoperability for Microwave Access (WiMAX), and Global System for Mobile Communications (GSM), among others. And this air-interface protocol may then define the structure of the cellular wireless network's air interface as well as the procedures for serving UEs over the air interface (e.g., registration, handover, scheduling, etc.)
In each of a base station's coverage areas, the base station may radiate to provide a frequency channel known as a “carrier” over which the base station may engage in air-interface communication with UEs operating in the coverage area, with this carrier comprising a downlink for carrying communications from the base stations to UEs and an uplink for carrying communications from UEs to the base stations. In practice, the carrier may operate on a particular carrier frequency or a particular pair of carrier frequencies. For instance, in an implementation known as frequency division duplex (FDD), the carrier may operate on a particular pair of carrier frequencies—one for the downlink and another for the uplink. Alternatively, in an implementation known as time division duplex (TDD) arrangement, the carrier may operate on a single carrier frequency, with the downlink and uplink being time-division multiplexed over this single carrier frequency.
The carrier's downlink and uplink may then be divided into discrete air-interface resources that may be used to carry control and/or bearer data between the base station and particular UEs. For example, in an OFDMA protocol such as LTE, the downlink may be divided in both the time and frequency domains into discrete “resource blocks,” which may be used to carry control and/or bearer data to UEs. In particular, in the time domain, the LTE downlink may be divided into transmission time intervals (TTIs), or sub-frames, that each have a duration of 1 millisecond (ms) and consist of two 0.5 ms timeslots. And in the frequency domain, the LTE downlink may be divided into groups of 12 sub-carriers that each have a bandwidth of 15 KHz (for a total group bandwidth of 180 kHz), with each group of sub-carriers in a given TTI timeslot defining a different resource block. Thus, in each TTI slot, the LTE downlink has a finite number of resource blocks that is limited by the downlink's channel bandwidth. The LTE uplink may have a similar configuration.
The LTE protocol may also define various channels that are mapped onto the resource blocks of the carrier's downlink and uplink. For instance, on the downlink, a first portion of time of each resource block in each TTI slot may define channels for use in carrying control signaling from the base station to UE, such a physical downlink control channel (PDCCH), a Physical Control Format Indicator Channel (PCFICH), and a Physical Hybrid-ARQ Indicator Channel (PHICH). Then, the remaining portion of each resource block in a given TTI slot (other than any portion reserved for reference symbol use or the like) may define a Physical Downlink Shared Channel (PDSCH) for use in carrying bearer data from the base station to UEs.
The LTE uplink may have channels that are mapped to the uplink resource blocks in a similar manner, including a Physical Uplink Control Channel (PUCCH) that primarily serves to carry control signaling from UEs to the base station, a Physical Random Access Channel (PRACH) that primarily serves to carry random access preambles from UEs to the base station, and a Physical Uplink Shared Channel (PUSCH) that primarily serves to carry bearer data from UEs to the base station.
In an LTE system arranged as above, when a UE enters into a coverage area of a base station, the UE may engage in attach signaling with the base station in order to register for service by the base station on the carrier provided in the coverage area. Through the attach process and/or subsequently, the base station and supporting LTE network infrastructure may establish one or more bearers for the UE, essentially defining logical tunnels for carrying bearer data between the UE and a transport network such as the Internet. Thereafter, the UE may operate either in an idle mode or a connected mode on the carrier.
In the idle mode, the UE may periodically monitor a downlink control channel (e.g., the PDCCH) on the carrier to receive overhead system information and to check for any page messages destined to the UE. If the UE then receives a page message intended for the UE and/or if the UE seeks to engage in bearer communication with the network, the UE may then transmit a random access preamble or other such request to the base station over an uplink control channel (e.g., the PRACH) of the carrier, to which the base station may respond by allocating certain PUSCH resources to the UE so that the UE can send a connection request. In turn, the UE may send a connection request to the base station, which serves to establish an air-interface “connection” between the UE the base station and cause the UE to begin operating in the connected mode.
While the UE is operating in the connected mode, the base station may then operate to schedule data communications with the UE on the carrier. For instance, when the base station has bearer data to transmit to the UE, the base station may seek to allocate particular PDSCH resources on the carrier for use to transmit that bearer data to the UE. In turn, the base station may transmit a “Downlink Control Information” (DCI) message to the UE over the PDCCH of the carrier, where this DCI message serves to identify the particular PDSCH resources of the carrier that have been allocated for the data transmission to the UE. Finally, the base station may transmit the bearer data using the allocated PDSCH resources on the carrier, and the UE may read the bearer data from these allocated PDSCH resources in accordance with the DCI message.
Similarly, when the UE has bearer data to transmit to the base station, the WCD may transmit a scheduling request to the base station and the base station may then seek to allocate particular PUSCH resources on the carrier for use to transmit the bearer data from the UE to the base station. In turn, the base station may transmit a DCI message to the UE over the PDCCH of the carrier, where this DCI message serves to identify the particular PUSCH resources of the carrier that have been allocated for the data transmission from the UE. Finally, in accordance with this DCI message, the UE may transmit the bearer data using the allocated PUSCH resources on the carrier.